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Ultra-Wide-Band SAW Sensors Based on Hyperbolically Frequency Modulated Signals

Authors:
Victor Plessky
Aleksei Shimko
You Jen Cho

Keywords: SAW sensors; hyperbolic frequency modulation; signal compression; reflecting grating; processing gain

Abstract:
A SAW (Surface Acoustic Wave) sensor including grooved-grating chirp reflectors is designed, manufactured and measured/probed on wafer. The device includes two wide-band SAW interdigital transducers (IDTs) on a YZ-cut LiNbO3 substrate, operating in the frequency range of 2000MHz-2500MHz (B=500MHz), situated in parallel acoustic tracks having two dispersive reflectors operating at the same frequencies. The reflector period increases linearly with distance from the IDTs and, correspondingly, the frequency of the impulse response of the reflectors is hyperbolically dependent on time. The duration of the impulse response is 1000ns, so that the signal base is B*T= 500. In remote measurements, such a sensor transforms interrogation signals received from the reader in its specific way and the reflected signals can be compressed such that the processing gain is greater than 20dB compared to other parasitic reflections. In contrast to classic Linear Frequency Modulated (LFM) signals, for the proposed signal, the compression process remains invariant with respect to the thermal expansion of the sensor, which significantly simplifies the “reading” algorithms. For the measurement of temperature, the device uses two offset reflectors, with the delay between the reflection peaks being dependent on temperature. At the moment of writing this paper, the different designs of the device were probed on wafer. Compressed signals are obtained with an expected duration of about 2 ns. We plan to package the sample devices and subsequently measure them remotely using a “reader” for measuring the S11(f) on the defined frequency grid.

Pages: 6 to 9

Copyright: Copyright (c) IARIA, 2018

Publication date: March 25, 2018

Published in: conference

ISSN: 2519-836X

ISBN: 978-1-61208-621-7

Location: Rome, Italy

Dates: from March 25, 2018 to March 29, 2018